Technical Field
The present invention relates to a nano-structure and a manufacturing process, and particularly to a visible light response photocatalyst structure and a process for manufacturing the same.
Related Art
Galvanic replacement reaction (GRR) is an old and versatile electrochemical reaction used for metallic transformation and has been widely adopted in engineering nano-composites. By utilizing the reduction potential difference within metals as driving force, metallic transformation can be completed in few minutes without any external energy applied in GRR.
The mechanism of sequential galvanic exchange and Kirkendall growth of polymetallic hollow nanoparticles. Various hollow metallic structures and metal-semiconductor junctions have been proposed via GRR, including Pt nanotubes, Au nanocages, Pt—Mn3O4, Pt—AgCl, Bi2Te3, Ag—Si, Au—Si, and etc.
The aforesaid hollow or composites structures covers almost all of the fields in chemistry, including methanol oxidation reaction (MOR), ethanol oxidation reaction (EOR), oxygen reduction reaction (ORR), surface enhanced Raman scattering (SERS), thermoelectric devices, degradation of pollutants, tumor detection, and etc.
Extending the GRR to the transformation between Mn3O4 and Fe2O3, this created more possibility for engineering novel nano-composites.
Silver-silver chloride (Ag—AgCl) composite has been utilized as visible-light active photo-catalyst recently because of the unique self-sensitized property. The direct band gap and indirect band gap of AgCl are 5.6 eV and 3.25 eV, respectively. As generally agreed, the presence of Ag enables a new electronic transition from the valance band of AgCl to the cluster energy levels of Ag, which is lower than the band gap of AgCl. This new energy gap enables visible-light response of Ag—AgCl composites.
The photo-generated holes combine with Cl— of AgCl and form chlorine radical (Cl0), and the photo-generated electrons then transfer to the ubiquitous oxygen in the electrolyte to form super oxygen radical (O2−). Both of them have strong capability for pollutant degradation.
A visible-light active AgCl—Ag composite sub-micron composite for MO degradation. Ag (core)-AgCl (shell) hybrid structure for the degradation of Rhodamine B (RhB). Recently, the evidence of hot electron transfer from Ag to AgCl under visible light irradiation.
Metallic complexes, e.g. PtCl62−, PdCl42−, AuCl4−, AuCl2−, and etc., are typical metallic precursors used in wet chemical process. The formation of AgCl(s) precipitate is consequently inevitable when adopting the aforesaid complexes to react with Ag in GRR. Most of previous studies deemed AgCl(s) as contamination.
Several processes have been proposed to remove AgCl(s), including NaCl wash, refluxing, and NH4OH(aq) wash. One dimensional Ag/AgCl/Au nanocomposites by reacting Ag with AuCl4− for ORR. The AgCl was utilized to stabilize the nanostructure, and the photo-response was not discussed. A galvanic replacement process transforming Ag/AgCl nanowires to Pt/AgCl nanotubes by utilizing H2PtCl6. Nevertheless, the photo-catalytic property of the Pt/AgCl composites was not reported neither. To our knowledge, there exist seldom prior arts that use GRR between metal and metallic precursors for preparing photo-catalysts.
That gave us a strong motivation to study photo-catalysts generated from GRR. A simple GRR was proposed to prepare AgCl modified Pt—Ag dendritic nanotubes (DNTs) for visible-light active photo-electrodes.
In view of the above, the prior art does not adopt the Galvanic GRR for manufacturing the light visible response photocatalyst structure, there is quite a need to set forth an improvement means to settle down this problem.